kconfig: add static qualifier to expand_string()

Now expand_string() is only used in preprocess.c
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/lkc_proto.h

@@ -58,7 +58,6 @@ void env_write_dep(FILE *f, const char *auto_conf_name);
 void variable_add(const char *name, const char *value,
 		  enum variable_flavor flavor);
 void variable_all_del(void);
-char *expand_string(const char *in);
 char *expand_dollar(const char **str);
 char *expand_one_token(const char **str);
 

scripts/kconfig/preprocess.c

@@ -15,6 +15,7 @@
 #define ARRAY_SIZE(arr)		(sizeof(arr) / sizeof((arr)[0]))
 
 static char *expand_string_with_args(const char *in, int argc, char *argv[]);
+static char *expand_string(const char *in);
 
 static void __attribute__((noreturn)) pperror(const char *format, ...)
 {
@@ -550,7 +551,7 @@ static char *expand_string_with_args(const char *in, int argc, char *argv[])
 	return __expand_string(&in, is_end_of_str, argc, argv);
 }
 
-char *expand_string(const char *in)
+static char *expand_string(const char *in)
 {
 	return expand_string_with_args(in, 0, NULL);
 }